(FORTUNE Magazine) – Pessimism can seem a virtue after this year's technology calamities--from the Great Northeastern Blackout to the plague of nasty computer worms. If you convince yourself that terrible things are going to happen to your computer, your precious data, and your expensive electronic gear, you may not be caught off guard when they actually do.

To get in an appropriately sour mood, start with this exercise: Unplug all your electronic toys, turn off the lights, and try to remember where you stored the candles and flashlights. (Wait. Bad idea. Turn up the lights just enough so that you can keep reading.) Ready? Okay, let's go through some drills.

PROBLEM ONE. A lightning bolt scores a direct hit on your laptop as you paddle up the piranha-infested Amazon in a canoe, plunging it and you into the water. Naturally your first thought is, Yikes! My memoir is on the hard disk!

Solution: This one's easy. If you survive, hike to the nearest pay phone and call DriveSavers (800-440-1904). The Novato, Calif., company boasts a 90% success rate in rescuing data from drowned, melted, gunshot, crushed, worn-out, infected, accidentally reformatted, and otherwise majorly abused hard disks. (The laptop shown in the photo above was the victim of a January house fire; its data were rescued. In the DriveSavers shop at presstime: a computer mashed by a car's airbag.) The service isn't cheap, typically $1,000 to get your precious data back, depending on such factors as turnaround time and what operating system your computer uses--er, used. John Christopher, a data-recovery engineer at the firm, urges people to visit the www.drivesavers.com site while they still can, to read such wise advice as "If your hard drive emits unusual noises (clicking, grinding, or metal scraping), turn it off immediately!" Trust these guys. But if you can, make a backup first.

PROBLEM TWO. Your computer suddenly seems constipated. Then, at midnight, it turns into a zombie and attacks the Pentagon. Men in black come and take away your family. You may have a worm, or a virus, or a Trojan horse.

Solution: Get a Macintosh. (The big reason Macs don't get targeted by virus writers is that Windows-based computers offer a more target-rich environment: There are at least 20 PCs out there for every Mac.) If you do depend on Windows, use protection. Do two things: First, click on the START tab and get familiar with "Windows Update." It's part of Microsoft's Trusted Computing initiative. You can trust that each week there'll be a new software patch to download so that you can fix a newly discovered hole in Windows.

Second, buy a copy of Symantec's Norton AntiVirus 2004 Professional ($70, ouch). There are lots of antivirus programs, but I trust Norton the most. Install it, use it, and let it check regularly for the latest virus signatures. Be sure to get the 2004 version, which hits the stores this month. Click "yes" when the program asks permission to check for updates automatically, and when your year of free updates expires, subscribe to next year's version at a discount. An antivirus program that hasn't been updated for a week or two is, if not worthless, certainly worth less. Besides scanning for and deleting viruses automatically, Antivirus catches spyware inserted into your computer by unscrupulous websites and the keystroke logging program your creepy neighbor installed when he came over to fix your computer.

If you're on an always-on Internet connection like a cable modem or DSL line, you also need a personal firewall, like Zone Labs' new Zone Alarm Pro 4.0 ($40, www.zonelabs.com). ZAP is almost painless to install and configure. It keeps naughty hackers from probing your PC for break-in points, commandeering it while you sleep, and attracting that visit by the men in black.

PROBLEM THREE. The electricity goes out suddenly.

Solution: You may need a UPS (uninterruptible power supply). A UPS is a box that (1) feeds uninterrupted power to your system if the power line strokes out, (2) protects against power surges, dips, and brownouts that can damage delicate electronic gear, and (3) actually extends the life of your stuff if you live in a building with old, ratty wiring (which is to say, New York City). My favorite brand is American Power Conversion (www.apcc.com); the company's website has tips to help you select the right model for your needs (typically $120 to $140). Don't pay extra for long battery life unless you're a compulsive worker; most blackouts last just a few minutes, and all you really need to buy is enough time to save your files and shut down gracefully. And don't plug your power strips or laser printer into a UPS. Just don't.

If the idea of being without juice for hours causes you anxiety, consider Honda's EU1000 portable gasoline-powered generator ($700; www.honda-powerequipment.com). It runs all your stuff for four hours on a half-gallon of gas. I recommended this puppy for Father's Day. Don't you wish you had listened?

PROBLEM FOUR. You dream that Ken Lay is the new Secretary of Energy.

Solution: Buy a good surge suppressor, not the $25 power strip that claims to protect your equipment but couldn't suppress a cough. In fact, buy lots of them and use them for your TV and stereo equipment and cable modem, not just your PC. They have feelings too, you know? Not as versatile as a UPS--but less expensive--a good surge suppressor will take the electron bullets aimed at your gear by lightning strikes or rogue behavior by the grid. (Cheap suppressors fail by responding too slowly, or letting too much voltage pass through, or dying after the first spike, leaving your equipment vulnerable to the next.) Even good surge suppressors have a serious downside: They don't help with brownouts, which can be just as damaging as power spikes. Another vexation: No two makers use the same measurements to allow a useful comparison. As a result, I just go with reliable brands. Besides American Power Conversion, I trust TrippLite (www.tripplite.com).

PROBLEM FIVE. Your computer is working perfectly. In other words, your hard disk is about to crash.

Solution: Hello? Didn't I tell you to back up your key files? NTI's Back-up Now! Deluxe Version 3.0 ($70, www.ntibackupnow.com) lets you copy your stuff onto disks or drives in almost any format, and works great, as long as you use it. Or try one of Maxtor's second-generation OneTouch external USB 2/Firewire hard drives ($200 to $400 depending on capacity, www.maxtor.com). They come with Dantz Retrospect Express 6.0 software. Backing up your main hard disk is as easy as one touch; you can also schedule regular back-up sessions. And because it is portable, you can keep it separate from your PC--just in case of fire, flood, or asteroid strike. Hey, you never know.